What has to be different to allow refraction to occur?AT.the medium.the lightS.the waveD.the speed
The speed of the wave should be different after it enters a fast medium to a slow medium bend. This is what causes the bending. The boundary where this difference takes place is where the refraction occurs. Read more on http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/refr.html.
idk what grade are you in is this a question or jibber jabber